In the manufacture of oil impregnated paper wrapped cables having copper or aluminum conductors, the cable conductor is first wrapped with a paper insulation. This paper insulation must then be thoroughly dried prior to oil impregnation. Drying is accomplished by passing a heating current through the cable conductor to heat and thereby dry the paper insulation along its inner surface and by subjecting the outer surface of the paper insulation to a dry heated atmosphere provided by steam jackets in a sealed tank.
During drying the cable temperature must be monitored regularly to insure that it does not exceed predetermined limits and damage the paper insulation. Prior art temperature measurement systems utilized for this purpose could only be used when no heating current was flowing in the conductor. This required that the heating current be interrupted periodically in order to monitor conductor temperature resulting in longer drying periods and more costly cable manufacture.
The present invention solves the above described problem by providing a temperature measuring system which can monitor cable temperature whether or not a heating current is flowing in the cable conductor.